Melatonin receptor subtype expression in human cerebellum

We report the distinct cellular distribution in the human cerebellar cortex of the mammalian mt₁ (Mel(1a)) and MT₂ (Mel(1b)) (1) melatonin receptor subtypes. Specific binding of the non-selective radioligand 2- [¹²⁵I]iodomelatonin to the outer molecular layer was significantly higher than to the granule cell layer. Melatonin receptor subtype expression was assessed by in situ hybridization using selective and specific digoxigenin- labeled antisense oligonucleotide probes. This is the first demonstration of MT₂ melatonin receptor mRNA expression in human cerebellar Bergmann glia and astrocytes. On the other hand, the mt₁ melatonin receptor mRNA was expressed in both basket-stellate cells and granule cells. We conclude that mt₁ and MT₂ melatonin receptors are heterogeneously expressed in human cerebellar cortex.